The Glycemic Index is a tool that measures how different foods affect blood glucose levels in the body within a few hours of eating. It was invented in 1981 by David Jenkins of the University of Toronto. His goal was to help people with diabetes choose foods that keep their blood sugar in balance. Once introduced, diet experts and nutritionists tested foods for their properties and influence on sugar levels. Hundreds of foods were added to the Index. It didn't take long for dieters to take advantage of the information the Glycemic Index provides.
To calculate the average GI value of a food, scientists measure how blood sugar changes over time. They use at least ten volunteers in order to create an average value. To be tested successfully, the food must have 50 grams of carbs at the start of the test. Subjects undergo blood tests at regular intervals over the following two hours to measure glucose content. A particular formula gives results and provides a relative ranking of each food.
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